1. Field of the Invention
The present invention relates generally to three terminal magnetic sensors such as spin valve transistor sensors for magnetic heads, and more particularly to a spin valve transistor sensor in which the base and collector are formed within the semiconductor layers of the sensor.
2. Description of the Prior Art
Magnetic heads for hard disk drives are generally fabricated with a read head portion and a write head portion. Currently, the typical read head portion of such magnetic heads includes a type of spin valve sensor that is referred to as a giant magnetoresistance (GMR) sensor. Such GMR sensors include two electrical signal leads, and changes in electrical resistance of layers within the GMR sensor caused by the presence of magnetic data bits proximate the read head modulate the current of the magnetic head electronic sensor circuit. The fabrication characteristics of such sensors are well known to those skilled in the art.
Efforts to create more sensitive read head sensors have recently lead to the development of three terminal magnetic sensors, such as spin valve transistor (SVT) sensors. In such devices, the components of a typical spin valve sensor are fabricated upon a semiconductor layer, and three electrical leads, emitter, base and collector are utilized. One such SVT sensor for a magnetic head is described in published U.S. Patent Application U.S. 2003/0214763 A1, published Nov. 20, 2003. The SVT sensors described in this published application include configurations in which the semiconductor is connected to the collector lead and components of the spin valve structure are connected to the emitter and base leads. The SVT sensor of the magnetic head of the present invention is fabricated with a different structure.